If the husband goes out of the house of the wife whose day it is and goes to the house of the other wife, that is subject to further discussion: 

(a)

If it is during the day, and the division is on the basis of nights, then it is permissible in case of need, such as dropping things off, handing over money for maintenance, finding out news, and visiting her if she is sick and so on, because of the hadeeth of ‘Aa’ishah (may Allaah be pleased with her) who said: The Messenger of Allaah (peace and blessings of Allaah be upon him) did not favour one of us over another with regard to division of his time and how long he stayed with us, and there was rarely a day when he did not go around to all of us, and he would draw close to each wife without having intercourse, until he reached the one whose day it was, then he would stay overnight with her. Sawdah bint Zam’ah said, when she grew old and feared that the Messenger of Allaah (peace and blessings of Allaah be upon him) would leave her: O Messenger of Allaah, my day is for ‘Aa’ishah; and the Messenger of Allaah (peace and blessings of Allaah be upon him) accepted that from her. Narrated by Abu Dawood (2135); al-Albaani said in Saheeh Abi Dawood: (it is) hasan saheeh. 

It is permissible for the husband to be intimate with his wife when he enters upon her, without having intercourse, because ‘Aa’ishah (may Allaah be pleased with her) said: The Messenger of Allaah (peace and blessings of Allaah be upon him) would enter upon me when it was the day of another of his wives, and he would do everything with me except intercourse. Classed as hasan by al-Albaani in Irwa’ al-Ghaleel (2023). 

He should not stay with her for long, and if he stays too long he should make it up to the one whose turn it is. 

(b)

As for going out to the other wife at night, it is not permissible except in case of necessity, such as if she is gravely ill, or giving birth and her contractions are severe, or there is fear of robbery and fire; if he stays with her too long then he should make it up to the one whose turn it is. 

Ibn Qudaamah (may Allaah have mercy on him) said: As for entering upon her co-wife when it is her turn: 

If it is at night, it is not permissible except in case of necessity, such as if she is dying, and he wants to be with her or she wants to give him final requests (a will), or something else that is essential. If he does do that, and he does not stay long before he leaves, he does not have to make it up. If he stays and the sick wife recovers, then he should make it up to the other wife, staying as long as he stayed with (the one who sick). 

If he goes there for something that is not necessary, he is sinning, and the ruling is that he should make it up, just as if he went there for a necessary reason, because there is no point in making up a short time. 

As for entering upon a wife during the day when it is the turn of another, that is permissible in the case of need, such as giving her maintenance, visiting her if she is sick, asking about something that he needs to know, or visiting her because he has not seen her for a while and so on, because of the report narrated by ‘Aa’ishah who said: The Messenger of Allaah (peace and blessings of Allaah be upon him) would enter upon me when it was the day of another of his wives, and he would do everything with me except intercourse. When he enters upon her, he should not have intercourse with her and he should not stay with her for long, because that means that he has dwelt with her and she is not entitled to that. 

If he stays too long with her, he should make it up (to the other wife). End quote from al-Mughni (7/234). 

Based on that, if the husband’s going to the house of the wife whose turn it is not happens by day, for the reason that you mention of checking on her, then there is no sin on him for that, and he should not stay there for a long time, except in case of necessity. If it happens at night, it is not permissible for him to go to her unless it is an emergency, such as if she is very sick or the wife whose turn it is gives him permission. If he stays there for a long time then he must make it up to the other wife, spending as long with her as he did with (the wife whose house he went to out of turn). 

And Allaah knows best.